Fix the race between PVC finalizer and snapshot finalizer removal

pkg/common-controller/snapshot_controller.go

@@ -182,7 +182,7 @@ func (ctrl *csiSnapshotCommonController) syncSnapshot(snapshot *crdv1.VolumeSnap
 	klog.V(5).Infof("syncSnapshot [%s]: check if we should remove finalizer on snapshot PVC source and remove it if we can", utils.SnapshotKey(snapshot))
 
 	// Check if we should remove finalizer on PVC and remove it if we can.
-	if err := ctrl.checkandRemovePVCFinalizer(snapshot); err != nil {
+	if err := ctrl.checkandRemovePVCFinalizer(snapshot, false); err != nil {
 		klog.Errorf("error check and remove PVC finalizer for snapshot [%s]: %v", snapshot.Name, err)
 		// Log an event and keep the original error from checkandRemovePVCFinalizer
 		ctrl.eventRecorder.Event(snapshot, v1.EventTypeWarning, "ErrorPVCFinalizer", "Error check and remove PVC Finalizer for VolumeSnapshot")
@@ -202,7 +202,7 @@ func (ctrl *csiSnapshotCommonController) syncSnapshot(snapshot *crdv1.VolumeSnap
 	// created from a PVC with a finalizer. This is to ensure that the PVC finalizer
 	// can be removed even if a delete snapshot request is received before create
 	// snapshot has completed.
-	if snapshot.ObjectMeta.DeletionTimestamp != nil && !ctrl.isPVCwithFinalizerInUseByCurrentSnapshot(snapshot) {
+	if snapshot.ObjectMeta.DeletionTimestamp != nil {
 		return ctrl.processSnapshotWithDeletionTimestamp(snapshot)
 	}
 
@@ -234,27 +234,6 @@ func (ctrl *csiSnapshotCommonController) syncSnapshot(snapshot *crdv1.VolumeSnap
 	return ctrl.syncReadySnapshot(snapshot)
 }
 
-// Check if PVC has a finalizer and if it is being used by the current snapshot as source.
-func (ctrl *csiSnapshotCommonController) isPVCwithFinalizerInUseByCurrentSnapshot(snapshot *crdv1.VolumeSnapshot) bool {
-	// Get snapshot source which is a PVC
-	pvc, err := ctrl.getClaimFromVolumeSnapshot(snapshot)
-	if err != nil {
-		klog.Infof("cannot get claim from snapshot [%s]: [%v] Claim may be deleted already.", snapshot.Name, err)
-		return false
-	}
-
-	// Check if there is a Finalizer on PVC. If not, return false
-	if !utils.ContainsString(pvc.ObjectMeta.Finalizers, utils.PVCFinalizer) {
-		return false
-	}
-
-	if !utils.IsSnapshotReady(snapshot) {
-		klog.V(2).Infof("PVC %s/%s is being used by snapshot %s/%s as source", pvc.Namespace, pvc.Name, snapshot.Namespace, snapshot.Name)
-		return true
-	}
-	return false
-}
-
 // processSnapshotWithDeletionTimestamp processes finalizers and deletes the content when appropriate. It has the following steps:
 // 1. Get the content which the to-be-deleted VolumeSnapshot points to and verifies bi-directional binding.
 // 2. Call checkandRemoveSnapshotFinalizersAndCheckandDeleteContent() with information obtained from step 1. This function name is very long but the name suggests what it does. It determines whether to remove finalizers on snapshot and whether to delete content.
@@ -858,7 +837,7 @@ func (ctrl *csiSnapshotCommonController) ensurePVCFinalizer(snapshot *crdv1.Volu
 }
 
 // removePVCFinalizer removes a Finalizer for VolumeSnapshot Source PVC.
-func (ctrl *csiSnapshotCommonController) removePVCFinalizer(pvc *v1.PersistentVolumeClaim, snapshot *crdv1.VolumeSnapshot) error {
+func (ctrl *csiSnapshotCommonController) removePVCFinalizer(pvc *v1.PersistentVolumeClaim) error {
 	// Get snapshot source which is a PVC
 	// TODO(xyang): We get PVC from informer but it may be outdated
 	// Should get it from API server directly before removing finalizer
@@ -874,8 +853,9 @@ func (ctrl *csiSnapshotCommonController) removePVCFinalizer(pvc *v1.PersistentVo
 	return nil
 }
 
-// isPVCBeingUsed checks if a PVC is being used as a source to create a snapshot
-func (ctrl *csiSnapshotCommonController) isPVCBeingUsed(pvc *v1.PersistentVolumeClaim, snapshot *crdv1.VolumeSnapshot) bool {
+// isPVCBeingUsed checks if a PVC is being used as a source to create a snapshot.
+// If skipCurrentSnapshot is true, skip checking if the current snapshot is using the PVC as source.
+func (ctrl *csiSnapshotCommonController) isPVCBeingUsed(pvc *v1.PersistentVolumeClaim, snapshot *crdv1.VolumeSnapshot, skipCurrentSnapshot bool) bool {
 	klog.V(5).Infof("Checking isPVCBeingUsed for snapshot [%s]", utils.SnapshotKey(snapshot))
 
 	// Going through snapshots in the cache (snapshotLister). If a snapshot's PVC source
@@ -886,6 +866,10 @@ func (ctrl *csiSnapshotCommonController) isPVCBeingUsed(pvc *v1.PersistentVolume
 		return false
 	}
 	for _, snap := range snapshots {
+		// Skip the current snapshot
+		if skipCurrentSnapshot && snap.Name == snapshot.Name {
+			continue
+		}
 		// Skip pre-provisioned snapshot without a PVC source
 		if snap.Spec.Source.PersistentVolumeClaimName == nil && snap.Spec.Source.VolumeSnapshotContentName != nil {
 			klog.V(4).Infof("Skipping static bound snapshot %s when checking PVC %s/%s", snap.Name, pvc.Namespace, pvc.Name)
@@ -902,8 +886,9 @@ func (ctrl *csiSnapshotCommonController) isPVCBeingUsed(pvc *v1.PersistentVolume
 }
 
 // checkandRemovePVCFinalizer checks if the snapshot source finalizer should be removed
-// and removed it if needed.
-func (ctrl *csiSnapshotCommonController) checkandRemovePVCFinalizer(snapshot *crdv1.VolumeSnapshot) error {
+// and removed it if needed. If skipCurrentSnapshot is true, skip checking if the current
+// snapshot is using the PVC as source.
+func (ctrl *csiSnapshotCommonController) checkandRemovePVCFinalizer(snapshot *crdv1.VolumeSnapshot, skipCurrentSnapshot bool) error {
 	if snapshot.Spec.Source.PersistentVolumeClaimName == nil {
 		// PVC finalizer is only needed for dynamic provisioning
 		return nil
@@ -922,10 +907,10 @@ func (ctrl *csiSnapshotCommonController) checkandRemovePVCFinalizer(snapshot *cr
 	if utils.ContainsString(pvc.ObjectMeta.Finalizers, utils.PVCFinalizer) {
 		// There is a Finalizer on PVC. Check if PVC is used
 		// and remove finalizer if it's not used.
-		inUse := ctrl.isPVCBeingUsed(pvc, snapshot)
+		inUse := ctrl.isPVCBeingUsed(pvc, snapshot, skipCurrentSnapshot)
 		if !inUse {
 			klog.Infof("checkandRemovePVCFinalizer[%s]: Remove Finalizer for PVC %s as it is not used by snapshots in creation", snapshot.Name, pvc.Name)
-			err = ctrl.removePVCFinalizer(pvc, snapshot)
+			err = ctrl.removePVCFinalizer(pvc)
 			if err != nil {
 				klog.Errorf("checkandRemovePVCFinalizer [%s]: removePVCFinalizer failed to remove finalizer %v", snapshot.Name, err)
 				return err
@@ -1325,6 +1310,16 @@ func (ctrl *csiSnapshotCommonController) removeSnapshotFinalizer(snapshot *crdv1
 		return nil
 	}
 
+	// If we are here, it means we are going to remove finalizers from the snapshot so that the snapshot can be deleted.
+	// We need to check if there is still PVC finalizer that needs to be removed before removing the snapshot finalizers.
+	// Once snapshot is deleted, there won't be any snapshot update event that can trigger the PVC finalizer removal.
+	if err := ctrl.checkandRemovePVCFinalizer(snapshot, true); err != nil {
+		klog.Errorf("removeSnapshotFinalizer: error check and remove PVC finalizer for snapshot [%s]: %v", snapshot.Name, err)
+		// Log an event and keep the original error from checkandRemovePVCFinalizer
+		ctrl.eventRecorder.Event(snapshot, v1.EventTypeWarning, "ErrorPVCFinalizer", "Error check and remove PVC Finalizer for VolumeSnapshot")
+		return newControllerUpdateError(snapshot.Name, err.Error())
+	}
+
 	snapshotClone := snapshot.DeepCopy()
 	if removeSourceFinalizer {
 		snapshotClone.ObjectMeta.Finalizers = utils.RemoveString(snapshotClone.ObjectMeta.Finalizers, utils.VolumeSnapshotAsSourceFinalizer)